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Pathogens on Farm and in Processing Related

01 July 2013

Salmonella and Campylobacter prevalence and loads on the farm are significantly associated with prevalence and loads of the same pathogens at processing.

The study on “Salmonella and Campylobacter in Broiler Chickens” by researchers at the University of Georgia, University of Arizona and University of Minnesota and published by the American Society for Microbiology shows that management practices that reduce pathogens on the farm would be expected to reduce contamination at processing.

Vaccination of breeder hens, competitive exclusion products, and the use of acidified water during feed withdrawal have all been reported to reduce Salmonella colonisation in commercial broiler flocks.

Unfortunately, the research team of Roy D. Berghaus, Stephan G. Thayer, Bibiana F. Law, Rita M. Mild, Charles L. Hofacre and Randall S. Singer said that, apart from the implementation of strict biosecurity protocols to reduce the likelihood of Campylobacter introduction, reliable approaches to reduce Campylobacter colonisation are currently unavailable.

As a post-processing intervention, freezing has been shown to reduce Campylobacter counts of broiler carcasses by 0.65 to 2.87 log10.

The researchers said that additional research is needed to develop and quantify the effectiveness of on-farm pathogen control methods in commercial production settings.

The prospective cohort study was performed to evaluate the prevalence and loads of Salmonella and Campylobacter in farm and processing plant samples collected from 55 commercial broiler chicken flocks.

Environmental samples were collected from broiler houses within 48 hours before to slaughter and carcass rinses were performed on birds from the same flocks at four different stages of processing.

Salmonella was detected in farm samples of 50 (90.9 per cent) flocks and in processing samples of 52 (94.5 per cent) flocks.

Campylobacter was detected in farm samples of 35 (63.6 per cent) flocks and in processing samples of 48 (87.3 per cent) flocks.

There was a significant positive relationship between environmental farm samples and processing plant carcass rinses with respect to both Salmonella and Campylobacter prevalence and loads, the study says.

Campylobacter loads were significantly higher than Salmonella loads and the correlations between samples collected from the same flocks were higher for Campylobacter than they were for Salmonella.

Boot socks were the most sensitive sample type for detection of Salmonella on the farm, whereas litter samples had the strongest association with Salmonella loads in pre-and post-chill carcass rinses.

Boot socks, drag swabs and faecal samples all had similar sensitivity for detecting Campylobacter on the farm, and all were more strongly associated with Campylobacter loads in carcass rinses than were litter samples.

Farm samples explained a greater proportion of the variability in carcass rinse prevalence and loads for Campylobacter than they did for Salmonella.

Salmonella and Campylobacter prevalence and loads both decreased significantly as birds progressed through the processing plant.

The researchers said that Salmonella and Campylobacter cause an estimated 1.9 million food-borne illnesses in the US each year, and poultry has been identified as a common source of both pathogens.

In another study, ranking the importance of 104 different pathogen-food combinations with respect to their combined impact on the total cost of illness and loss of quality-adjusted life years, Campylobacter and Salmonella infections from poultry ranked first and fourth, respectively.

The regulatory approach to foodborne pathogen control in the US broiler chicken industry is focused primarily on processing plants.

A Salmonella performance standard was introduced in 1996, along with a requirement for slaughter establishments to implement a Hazard Analysis and Critical Control Points (HACCP) programme for pathogen reduction.

While the 50 per cent of Salmonella-positive broiler carcasses identified by regulatory testing decreased from an initial baseline prevalence of 20 per cent in 1996 to 6.5 per cent in 2011, the incidence of human Salmonella infections remained essentially unchanged over the same period of time.

Consequently, a more stringent Salmonella performance standard was introduced in 2011, along with a new performance standard for Campylobacter, the research points out.

Processing plant interventions such as the use of chlorinated water during immersion chilling were seen as effective at reducing microbial contamination of broiler carcasses although the magnitude of the reductions that can be achieved with these methods is limited.

Pre-harvest management practices with the potential to reduce pathogen contamination on the farm have been recommended as a way to provide a more integrated approach to pathogen control.

Specific practices recommended by the US Department of Agriculture’s Food Safety Inspection Service (USDA FSIS) for pre-harvest pathogen control in broiler chickens include:

having stringent biosecurity measures and sanitation practices

controlling litter moisture

using well-timed feed withdrawal prior to slaughter

using acids in drinking water during feed withdrawal

using vaccination programmes, and

screening flocks for pathogens prior to processing.

The research team said that although it seems reasonable that pathogen contamination on the farm would be associated with pathogen contamination at processing, there is currently little quantitative information available with respect to the relationships between these two environments.

For Salmonella in particular, traditional enumeration methods are laborious and infrequently used in poultry processing studies.

The lack of available information on pathogen concentrations has been identified as an important data gap with respect to evaluating the effectiveness of intervention and control measures in primary poultry production and processing.

The primary objectives of this study were to obtain comparative information on the distribution of Salmonella and Campylobacter prevalence and loads in commercial broiler chicken flocks, and to quantify the relationships between pathogen prevalence and loads in farm and processing plant samples.